The invention relates to a drainage device and more particularly to a drainage device which is designed to drain fluids from a body cavity such as the pleural cavity and to measure the flow of air through the drainage device.
It is essential for normal breathing that the space within the pleural cavity surrounding the lungs be free of liquid and be subject to a negative pressure so as to draw the lungs outwardly to fill this pleural cavity in order to permit proper breathing. Any invasion of the pleural cavity such as by lung surgery or foreign objects which pierce the ribcage or, for example, where the patient has pleurisy, generates fluids in the pleural cavity which tend to obstruct normal breathing operations. It is necessary to provide a device which can remove these fluids from the pleural cavity and, at the same time, ensure that the desired degree of negative pressure is maintained within the pleural cavity.
One of the basic types of apparatus which have been used for this purpose is shown, for example, in U.S. Pat. Nos. 3,363,626 and 3,363,627. This apparatus is known as an underwater drainage apparatus and provides three chambers, one chamber comprising a collection chamber for collecting the fluids drained from the pleural cavity through a thoracotomy tube, a second chamber known as an underwater seal chamber which protects the pleural cavity from being subject to atmospheric pressure, and a third chamber known as a pressure manometer chamber which serves to regulate the degree of negative pressure within the pleural cavity. This type of apparatus has been highly successful in both removing fluids from the pleural cavity and in maintaining the desired degree of negativity within the pleural cavity. However, such an apparatus required prefilling the underwater seal chamber with water and also prefilling the pressure manometer chamber to the desired level to maintain the desired degree of negativity within the pleural cavity. Thus, there has been a need for a drainage device which could be attached to the patient's pleural cavity and which provided a simplified structure not requiring a vacuum pump. For example, in emergency situations in the field where a vacuum pump may not be available, it is necessary to provide a device which can be attached to a patient's pleural cavity to permit drainage of fluids to allow the lungs to expand.
The drainage system disclosed in U.S. Pat. No. 4,015,603 provided an apparatus which may or may not be used with a vacuum source. The underwater seal in this system is located at the lower end of the thoracotomy tube at the upper end of the drainage device. In the device shown in this prior patent, the underwater seal is formed by liquid drained from the patient's pleural cavity. The location of the underwater seal chamber at the lower end of the thoracotomy tube as disclosed in U.S. Pat. No. 4,015,603 created a problem in certain unusual circumstances. In a case of a patient having a blockage in the bronchial tubes, such that the patient was having severe problems in getting air into the lungs, exceedingly high negativity was being created in the pleural cavity. Such high negativity caused the fluid in the underwater seal to be drawn upwardly through the thoracotomy tube and, if the degree of negativity was sufficiently high, it was possible for fluid to reenter the pleural cavity. This condition of fluid from the underwater seal chamber reentering the pleural cavity could cause infection or otherwise create problems for the patient. In addition, it was possible to entirely lose the seal provided by the underwater seal chamber during periods of high negativity in the pleural cavity. The loss of the water seal has a potential for serious damage in the event the suction becomes disconnected or the device is used as a two bottle system with the collection chamber open to atmosphere.
In U.S. Pat. No. 3,853,128 there is disclosed a positive pressure relief valve in a drainage apparatus having a conventional underwater seal and manometer chamber. The positive pressure relief valve is disposed between the underwater seal and manometer chambers and provides relief from high pressure surges within the collection chamber. The device disclosed in U.S. Pat. No. 3,853,128 must, however, be prefilled prior to use and does not function as a two chambered device which is usable without prefilling. In U.S. Pat. No. 3,559,647 there is disclosed an underwater drainage apparatus having seal which is provided with a gas flow meter at the bottom of the seal. The gas flow meter is comprised of a series of orifices located at the bottom of the underwater seal. The more orifices which gas passes through, the greater the gas flow. However, this type of flow meter is suitable only for indicating the gas flow in steps.